Lapping tool



C. E. ARCHER LAPPING TOOL Filed. March 13, 1947 @Qw-ramaam oriented Sept. 13, 1949 LAPPIN G TOOL Charles E. Archer, Birmingham, Mich., assignor to Ex-Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application March 13, 1947, Serial No. 734,410

4 Claims. ((31. 51-1843) 2 1 The present invention relates to abrading or U. S. Patent No. 2,268,479 to Paul R. Gjertsen. lapping tools for removing material from cy- Broadly, the device comprises an elongated manlindrical bores, and is specifically applicable to a drel H, together with a pair of abrasive holding tool assembly comprising a tapered mandrel asshoes 12 and associated abrading elements [3. sociated with a plurality of abrading members The mandrel has a shank end I4 WhlCh may be which are adjustable radially in response to ax1al shdably keyed in the spmdle l5 of the chuck for displacement of the mandrel with respect theredriving ingagoiment tlgerfwi ttlli i LimitieclG aziilal a21- to. In a device of this charac er, the work is l'us men of e man re W1 respec o e r generally positioned on the tool while the latter maining parts of the tool is obtained by clampis contracted radially, whereupon the tool is exing against thee end of the sptllllldlg I5t a pgir c? r3- panded to size for the lapping operation. aining lugs comprising e en en s 0 a One of the objects of the invention is to prolusting wires or rods l1 for the holding shoes !2. Vide a lapping tool of the foregoing type which In the present instance, this is accomplished by will be particularly well suited for use on small p s fl the 111gS between a sleeve 18 a diameter work where a high degree of accuracy is ahwashgr lfitakilnd r ll 2 3 5 D s t f tly i all g required. e en 0 e spin e y means 0 a re alnin Another object is to provide a lapping 13 1 f nut 26 threaded thereon. 130th the sleeve and the type described comprising novel and improved the Washer are p j d 'WIth Central bores of means for mounting abrading elements of unip p r sue to obtain a slld n fit 0n e a d form size and shape throughout their lengths. a s s p o d d wh e the oo ay be A further object of the present invention is to Fil l'lo uwo t 0; a l ifgks ggtgg tg ligngt provide a new and improved lapping tool of the E. S D9 m a C foregoing character which is light in weight and ls f s a t gy i t ;1; g a g strong, yet susceptible of easy and economical accomp 1S 6 111 e P e em 0 1m manufacture, utilizing a stepped construction in the elongated Other objects and advantages will become apihg the mandrel l l. Accordingly, parent as the following description proceeds, and gitg ggi g t gpg rigii el g a d gggs l l al c nf a l l g from the accom anyin drawings, in which: 5 i

Fggure 1 is 3 axialgsectional View of an tapered transition portion 22, and a tool-carrying sembled tool embodying the features of the in- Portion The diameter of j mandrelloody vention together with the essential portions of fi g fg g gsgpi ggg gi sfig pfiggggigggg; the su portin means.

Fig. is an inlarged axial sectional view of the is r d with a pair of diamfatyicauy opposed projecting end of the tool, showing in detail the ig g g fi ggzg f f ggg g 2 5 ;311: 3 holding shoes, the abrasive elements, and the i mnildrel body s 5 lager giaduafny g t gif portion of the mandrel. ward the transition portion or step 22 as shown igs. 3, 4 and 5 are transverse sectional views, in Figure 1 The taper of the transition Step 22 gi lmes and respectlvely which connects the body 2| and the outermost f th b 40 portion 23, is greater than that of the portion 2i h 55' f perspec We View of oneo ea mslve due to the substantial difference between the o Des per diameters of the mandrel body and the portion 23.

Afuhough an exemplaiy embodlment The outermost or projecting end portion 23 of Ven ion a been mus rated and descnbed the mandrel is basically an elongated cylinder W will, It h u be lmdersitood that 1S provided with diametrically opposed, longitudino Ion to the 9 to the specific nal grooves 25, mutually inclined at a small angle form disclosed, the intention being, on the co to the mandrel axis and disposed in alinement Mary to n modlfifatlons alternative with the grooves 24 of the mandrel body. The constructions fall1ng within thesplrit and scope grooves 5 are adapted to drivingly support the of T mventlon as expressed 1n the appended abrasive holding shoes l2, which are slidably claims. I keyed therein, and at the-same time to enable the ing mor sp lfi al y t h d aw the shoes to expand radially in response to an axial invention is there exempllfied in a 000 a apted displacement of the mandrel. Each of the grooves for coaxial mounting in a rotary tool support is given the contour of an elongate secantial cysuch as a chuck l0 after the manner shown in lindrical segment, creating within this portion of the mandrel an elongated wedge with laterally curved, inclined surfaces. The profile of this wedge, taken on a longitudinal plane passing through the mandrel axis and the center lines of the grooves, is clearly shown in Fig. 2. Profiles taken along other planes, parallel to the foregoing but laterally offset therefrom will also be Wedge-shaped. The closer such profiles are taken to the edges of the grooves,'the greater will be the thickness of the wedge sections, due to the lateral concavity of the surfaces of the wedge. Referring to Figs. 3, 4, and 5, it will be seen that transverse sections through the portion 23 define circular areas in which other circles have been partially points. Although the transverse cross-sectional area of the mandrel generally decreases toward the projecting end, it is evident that the greatest possible amount of stock has been allowed to remain in the portion 23, and. that such stock has been disposedin a manner providing a maximum of resistance to lateral :iiexure. The behavior of the portion 23in resisting-bending or lateral flex ore is somewhatanaiogousrto that'of a cantileversupported I-beam.

Closely associated-with the tool-carrying portion 23 of the mandrel. H, and having tapered surf-aces 26 adapted to enter into complemental engagement with those-of the grooves 25, are the abrasive holding shoes 12. Due to the fact that F71 these surfaces are alltakenif-rom segments of the same cylinder, thelongitudinal geometrical elements of the abutting grooves and shoe surfaces at each side of the axis of rotation are parallel with each other. Free longitudinal sliding movement between such surfaces is therefore readily obtainable and is utilizedin the operation of the tool. It will be appreciated from the foregoing that the abrasive holding shoes may be spread apart radially in response to an axial displace ment of the mandrel with respect to the shoes, or they may be permitted to move toward each other in response to an axial'displacement of the mandrel in the opposite'direction.

Near the outermostior larger ends of the holding shoes I2, meansisprovided'for receiving and carrying the abrasive elements 13 which are of uniform cross-section throughout their length. In the present instance, such means comprises a stepportion 27 having aplane surface parallel to the mandrel axis and towhich an abrasive element l3 maybe'bondediin any suitable manner. Preferably, the elements I3'are given the shape of cylindrical segments of uniform thickness, their dimensionsbeing determined in proportion to the size of the bore B inthe workpiece W.

At their innermost or smaller ends, the external surfaces of the shoes 12. areeachformed with a raised step portion 28 to which the associated one of the adjusting rods [1 is rigidly attached. In the embodiment illustrated; the step 28 has a flat surface and the rod is secured thereto as by welding or brazing, the point of attachment being within or facing the arc defined by the tapered surface of the shoe.

Intermediate the-steps Hand 28 each shoe 92 has an outer rounded offportion 29. The radius of curvature of this portion is slightly less than that of the abrading element i3 in order to allow sufiicient clearance between the shoe structure and the bore of the workpiece.

In operation, a'workpiece-having a bore to be lapped is positioned'on the tool while the latter is in the radially contracted-position. The mandrel inscribed at diametrically opposite '4 H is thereupon shifted axially toward the workpiece W, gradually moving the holding shoes l2 radially outward and bringing the abrading elements I3 into lapping engagement with the internal surface of the bore B. The tool is then rotated While the work is held stationary, until the bore has been lapped to the diameter for which the mandrel has been set. At this point, the mandrel may be shifted axially in the opposite direction and the shoes, together with their abrading elements thereupon will be permitted to move radially inward.

I claim as my invention:

1. In a radially expandible abrading device of the type which is expanded or contracted in response to relative axial movement between its parts, the combination comprising a mandrel having an elongated body portion of suitable cross-sectional area to permit said mandrel to be slidably keyed in a tool support, said mandrel also having a projecting end portion in the form of an elongated wedge with laterally concave and longitudinally inclined surfaces formed by diametrically opposed mutually inclined grooves in the shape of secantial cylindrical segments, abrasive holding shoes having surfaces adapted for complemental and abutting-engagement with said surfaces of said grooves, abrading elements carried by said holding shoes near their outermost ends and bonded thereto, saidabrading elements being in the form of cylindrical'segments of uniform thickness, andadjusting rods recessed in said body portion of said mandrel and rigidly attached to said holding shoes adjacent the innermost ends thereof, said rods having bent ends engageable by said tool support.

2. A radially expandible lapping tool having a mandrel comprising the combination of an elongated body portion adapted to be slidably keyed in a tool support, aconically tapered transition portion adjacent said body portion, a projecting end portion of: substantially smaller crosssectional area than said'body portion and located adjacent said transition portion, said projecting end portion including an elongate wedge having laterally concave andlongitudinally inclined surfaces defined by a pair ofdiametrically opposed grooves in the form of secantial cylindrical segments.

3. In a radially expandible lapping device of the type wherein abrasive holding shoes are slidably keyed to a grooved mandrel, the combination comprising a shoe having an elongate tapered surface adapted for sliding and abutting engagement with a complemental groove in'said mandrel, said surface being in the form of a secantial cylindrical segment, a fiat step portion in said shoe adjacent the larger end thereof for receiving an abrading element, a raised step portion on said shoe adjacent the smaller end thereof and adapted to be rigidly secured to an adjusting rod, and a rounded, off portion intermediate said step portions,

4. In a radially expandible lapping device of the type wherein a pair of abrasive holding shoes are slidably keyed to a grooved mandrel, the combination comprising an abrasive holding shoe having an elongate tapered surface adapted for sliding and abutting engagement with a complemental groove in said mandrel, said surface being in the formof an elongated cylindrical segment, a flat step portion inusaid shoe adjacent one end thereof for receiving an abrading element,, a raised step portion insaid' shoe adjacent the opposite end thereof for engagement with an REFERENCES CITED adjusting rod, a rounded off portion disposed intermediate said step portions, an abrading element in the form of a cylindrical segment of uniform thickness and adapted to be bonded to said UNITED STATES PATENTS fiat step portion, the radius of curvature of said abrading element being slightly greater than that 3 ggg g j of said rounded ofi portion, and an adjusting rod 2419136 Hasty 1947 rigidly secured to said raised step portion.

CHARLES E. ARCHER. 10

The following references are of record in the file of this patent: 

